1. Field of the Invention
The present invention relates to a position controlling device, and more particularly to a position controlling device for a carpenter angle drill/hollow chisel mortiser that can automatically stop an actuation of the carpenter angle drill when a moving base of the carpenter angle drill moves to a top dead center of the carpenter angle drill.
2. Description of Related Art
A conventional carpenter angle drill/hollow chisel mortiser is used to drill holes in a working piece, and has a base, a mounting stud, a moving head, a drill seat, a motor, an operating lever, and a position controlling device. The mounting stud is securely mounted on the base. The moving head is slidably mounted on a front side of the mounting stud above the base. The drill seat is securely mounted on a bottom of the moving head and has a drill. The motor is mounted on the moving base to drive the drill to rotate.
The operating lever is connected to the mounting stud to make the moving head slide relative to the mounting stud to enable the drill to move closer to or away from the base to drill the working piece. The position controlling device is mounted between the mounting stud and the moving head to provide a stroke of the drill, and has a bridge bar, two limiting blocks and a retaining arm. The bridge bar is mounted on a sidewall of the mounting stud. The limiting blocks are mounted around the bridge bar at an interval, and the interval may be equal to the stroke of the drill. The retaining arm is securely connected to the moving head, movably extends between the limiting blocks, and selectively abuts the limiting blocks.
In use, a user can adjust the stroke of the drill by changing the interval between the limiting blocks according to a thickness of the working piece. Then, the user rotates the operating lever, the drill is moved downwardly with the moving head to drill the working piece, and the drill is stopped to move downwardly when the retaining arm contacts the lower limiting block. After drilling the working piece, the drill is moved upwardly with the moving head and the operating lever and is stopped from moving upwardly when the retaining arm contacts the upper limiting block. Therefore, the stroke of the drill is limited between the limiting blocks since the retaining arm is moved between the limiting blocks.
However, the drill is driven by the motor, and the motor is actuated during the drill operation including a down stroke and an upstroke of the drill, and this means the drill is still rotated when the retaining arm contacts the upper limiting block. Then, the user or other persons may get injured by the rotating drill when completing the drill operation, and this is unsafe in use and will waste energy. In addition, the limiting blocks are only mounted around the bridge bar, and the retaining arm may hit the limiting blocks during the drilling operation to change the positions of the limiting blocks relative to the bridge bar, and this will change the interval between the limiting blocks. Then, the stroke of the drill will be changed and this will influence the processing quality of the conventional carpenter angle drill/hollow chisel mortiser.
To overcome the shortcomings, the present invention provides a position controlling device for a carpenter angle drill/hollow chisel mortiser to mitigate or obviate the aforementioned problems.